You can either swap weapons about 3/4 of the way through savage leap so you don't get the "pull down effect" and keep your forward momentum, or jump and use Savage Leap at almost the same time (very hard to do).

Firstly, make sure everyone in your party is using Powerful Potion of Undead Slaying and either Plate of Truffle Steak or Bowl of Curry Butternut Squash Soup. Also, make sure you have enough Dwayna's tears for the person in the group with the least DPS to throw on petrified people. Ideally, you'll want people to bring and trait for as much damage as possible.

There is also another bug with the sparks. If you pull less than 5 sparks to the middle of the room and then let Dwayna regenerate to full health, you will only need to pull the difference to the middle next time she stealths. So the trick is to pull 4 sparks to the middle, let her regenerate, and then get ready to DPS her as soon as a single spark is pulled to the middle. If this is done fast enough, you can push her past the 50% health stealth trigger, where her stealth ability will then become timer based.

Stability also works against petrification. Having a guardian use Stand your ground or Hallowed ground is a big help during that fight.